First question; on the topic of Carla's grenades, do certain rounds do more damage depending on the enemies? In the classic games I had always assumed incendiary > acid > explosive but I'm not sure anymore. Is nitrogen best overall like incendiary was imho or does each type of round serve a purpose?
Second question; is there a difficulty curve depending on which two characters are chosen for the mercenary round? I consider myself a cut above average but every once in awhile it seems like dogs and other select creatures are just harder to shake than they were the rounds before and rounds after. Sometimes I'll get tackled from behind by one of the first dogs in "Mining the Depths" and that son of a *****; no pun intended; is latched on and just as hard to shake as one that would have grabbed me in the closing minute the round before hand.
Damage wise, it is explosive > acid > nitrogen, but they serve different purposes, for the most part. Explosive should be used to kill the more bulky enemies (whoppers, napad's, etc) or to save a combo, acids are great for setting up certain enemies for coup de graces (grasshopper J'avo, bloodshots), and nitrogen are just good all around rounds that can be used to get rid of the more annoying enemies, such as magnum zombies, or get melee time off of enemies that are difficult to get time off of otherwise, such as the exploding ones. Besides those purposes, Carla can take care of normal enemies just fine with her picador.
No, the difficulty curve doesn't adjust depending on who is chosen, but certain characters have superior loadouts and melees to others on some stages. I believe the QTEs are more difficult later on in the match, but it shouldn't be too difficult to get dogs off in the start. Are you shaking both sticks?
Nitrogen rounds are excellent against most lower class enemies (zombies, J'avo + mutations) as frozen enemies that are killed by a melee attack award 5 seconds each. Even boss enemies can be frozen (Napad's) and will take massive damage from any form of attack. Acid rounds are useful for setting up CDG's on Bloodshots, killing Genzdo bosses (bee boss), and setting standard melee attacks on J'avo. Explosive rounds are boss killers and combo savers.
Standard grenades are good for crowd control as well as a massively huge exploit during a CDG animation. Just set up an enemy for a CDG, toss a hand grenade into a nearby crowd, wait about 1 second and then preform the CDG on your stunned enemy. While the CDG animation is playing out, all enemies killed by the hand grenade will count as a CDG kill (gaining you countless seconds in a single CDG). Incendiary grenades are great for killing Bloodshots or weaker zombies and flash grenades are good for setting up CDG's on Bloodshots and J'avo.
Hoped this helped mate. --- Stupidity isn't a virus, but it sure is spreading like one!